Apparatus and method for exchanging heat between solid materials and a fluid medium



Sept. 4. 1956 K J. SYLVEST 2 761,668

. a APPARATUS AND METHOD FOR EXCHANGING HEAT BETWEEN SOLID MATERIALS AND A FLUID MEDIUM Filed Dec. 12. 1951 4 Sheets-Sheet 1 70 FM 5 mm mvr NVENTOR ATTORNEYS Sept. 4. 1956 Filed Dec. 12, 1951 K. J. SYLVEST APPARATUS AND METHOD FOR EXCHANGING HEAT BETWEEN SOLID MATERIALS AND A FLUID MEDIUM 4 Sheets-Sheet 2 oooooooo oo 00 00 0 INVENTOR Sept. 4. 1956 K. J. SYLVEST 2,751,668

APPARATUS AND METHOD FOR EXCHANGING HEAT BETWEEN SOLID MATERIALS AND A FLUID MEDIUM Filed Dec. 12. 1951 4 Sheets-Sheet 3 INVENTOR 47M 25/65!" z ijlwajfim MM ATTORNEYS Sept. 4. 1956 K. J. SYLVEST 2,761,668

APPARATUS AND METHOD FOR EXCHANGING HEAT BETWEEN SOLID MATERIALS AND A FLUID MEDIUM Filed Dec. 12, 1951 4 Sheets-Sheet 4 WHTER INLET United States Patent APPARATUS AND METHOD FOR EXCHANGENG HEAT BETWEEN SOLID MATERIALS AND A FLUIDNIEDIUM Karl Jens Sylvest, Copenhagen, Denmark, assign-Jr to F. L. Smrdth & C0., New York, N. Y a corporation of New Jersey Application December 12, 1951, Serial No. 261,293 Claims priority, application Denmark December 13, 1950 Claims. (Cl. 263-32) This invention relates to heat exchange between a flowing medium in gaseous or liquid form and a pulverulent material capable of being rendered fluent by injection into it of air or another gas. More particularly, the invention is concerned with a novel method for exchanging heat between a flowing medium and finely divided material and with apparatus, by which the method can advantageously be practiced.

At the present time, various methods for altering the heat content of pulverulent material by means of a flowing medium have been developed and put into use, as for example, the material may be heated or cooled by being advanced in a thin layer along a wall, on the opposite side of which the treating medium flows in direct contact with the wall. In another form of indirect heat exchange, the material is conveyed through tubes in a constant state of agitation and the treating medium sweeps over the outer surfaces of the tubes. In one method of direct heat exchange, which has been put into practical use, the material is maintained as a bed, through which the treating medium is caused to pass. While these various methods are useful for some applications, they are not satisfactory, when large quantities of pulverulent material are to be heated or cooled, because of the small capacity of apparatus for practicing such methods.

The present invention is, accordingly, directed to the provision of a method of heat exchange between a pulverulent material and a flowing medium, by the use of which such heat exchange may be efliciently carried on, so that large quantities of material may be treated in relatively small apparatus. prehends various forms of apparatus suitable for the prac tice of the method.

In the treatment of pulverulent material toalter its heat content by means of a flowing medium in accordance with the new method, thematerial is fluidized by injection of air and then caused to flow through atortuous path in indirect contact'with the medium. The medium may be passed through passages, such as banks of small tubes, along the outer surfaces of which the fluidized material flows, and, because of the fluent condition of the material and the good contact betweenall parts of the material and the surfaces, a highly effective heat exchange isv obtained. 1

In the practice of the. method of the invention, it is advantageousto cause thetluidized material to flow along a tortuous path having vertical bends, so that the material flows alternately upwardly and downwardly. The auxiliary air for aerating the material may then be introduced through the surfaces, where a change in direction of the material occurs, so that the aeration is etfected at a plurality of points distributed along the course of the material. The aeration may be varied in intensity at the differentpoihts in accordance with a cycle, with the result that, at any instant during the cycle, powerful aeration may take place at one point, with littleor no aeration occurring elsewhere, after which the intense aeration occurs at another point with little or no aeration elsewhere.

The invention further com- In practical operation, it has been found that, by carrying on the intense aeration successively at different points, a substantial economy in the amount of air required is effccted, particularly when the aeration is carried on in such manner as to accelerate the travel of the material along the path.

The apparatus for practicing the new method may take various forms and, for example, may comprise a container provided with an inlet and an outlet fcr material, together with means for sub-dividing the interior of the container into a plurality of compartments connected together to form the tortuous passage above mentioned. The container is also provided with a system of passages in the form of tubes, channels, etc., through which the treating medium may flow out of direct contact with the material. The container is provided with means for admission of auxiliary air for aerating purposes, and the container is also provided with an air outlet at its top and containing a filter, through which the auxiliary air may escape. The container, preferably, includes a number of wholly or partially separated sections, across which the passages for the treating medium extend, the fluidized material flowing through the sections successively. With this arrangement it is easy to clean the passages for the medium and also to remove impurities, such as dust, which the medium may carry with it. Preferably, the arrangement of the.

compartments within the container and of the passages for the medium are so arranged that the medium flows generally countercurrent to the direction in which the material is traveling.

The passages for the flowing medium may advantageously be formed of banks of small diameter tubes closely spaced in rows with the tubes in one row staggered in relation to those in the adjacent rows. The ends of aligned tube banks are separated and the space between them may then be provided withan outlet, through which dust and other impurities in the treating medium may be collected for periodic removal.

The aerating means may take the form of nozzles or of porous plates of ceramic material forming closures for air chambers, into which the auxiliary air is admitted. The air supplied to the chambers and escaping through the plates is divided into fine streams, which penetrate the pulverulent material and effectively fluidize it. The aerating air may be supplied to respective nozzles or chambers under the control of valves, which can be operated to effect high intensity aeration at different points, as above set forth.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which Fig. 1 is a view, partly in vertical section on the line 11 of Fig. 2 and partly in elevation, of one form of apparatus for practising the invention in the preliminary heat treatment of a pulverulent cement raw material mix to be supplied to a rotary kiln;

Figs. 2, 3, 4, and 5 are sectional views on the lines 2- 2,

, 3-3, 4-4, and 55, respectively, of Fig. 1;

Fig. 12 is a diagrammatic view of means for operating valves controlling the admission of aerating air in accordance with a cycle.

In the installation shown in Fig. 1, the heat exchanger, generally designated 20, is employed in the preliminary heating of a p-ulverulent cement raw material mix, which is to be burned in a rotary kiln 21. The heat exchanger comprises a closed container 22 having an inlet 23 at its top for admission of material and an outlet 24 for the material through one side wall. The material is conducted from a source of supply to the inlet through a conduit 25 and the material discharged from the container is conducted through a conduit 26 into the upper end of the kiln, the conduit extending through the usual hood 27, into which the upper end of the kiln projects. At its top, the container is provided with outlets 28 for auxiliary air, each outlet containing a filter.

The space Within the container is sub-divided into a plurality of compartments connected together to form a tortuous passage from the inlet to the material outlet and, in the construction illustrated, the container is provided with a central longitudinal partition 29, extending from top to bottom of the container. The inlet 23 leads into a main compartment 30 at one side of the partition and the outlet 24 is formed in an outer Wall of the container, which partly defines the main compartment 31 at the other side of the partition. Main compartments 30 and 31 are both sub-divided by transverse walls and partitions into sub-compartments as follows. Spaced vertical transverse walls 32, 33 extend from about the middle of each main compartment through the bottom of the con tainer and define a sub-compartment 34. On opposite sides of the sub-compartment 34, each main compartment 30, 31 is sub-divided by transverse vertical partitions 35, 36, which terminate below the top and above the bottom of the main compartment.

The bottom 37 of the container on each side of the central partition 29 is imperforate, and it carries a plurality of short, upright partitions 38, on which are mounted porous plates 39 forming the top closures of air chambers 40. Air under pressure is conducted through a line 41 from a source of supply to a header 42, which are connected to the individual chambers through branches 43 containing valves 44, which may be electrically operated by solenoids 45 (Fig. 12). An air chamber 46 closed by a porous plate 47 is also mounted at the top of each sub-compartment 34, and each air chamber 46 is supplied with air through a valved branch from the header 42. Partition 29 is formed with an opening 48 near the end remote from the inlet 23, the opening lying near the tops of partitions 35, 36.

Tubes 49 are mounted in openings in the end wall 50 of the container and in walls 32, on each side of the partition 29. ()ther tubes 51 are mounted on each side of partition 29 in openings in wall 33 and in the end wall 52 of the container. The tubes in each bank or group are arranged in horizontal rows with the tubes in one row staggered in relation to those in the adjacent rows. A casing 53 is mounted in contact with the outer surface of wall 50 of the container to enclose the ends of the tubes mounted in openings in that wall, and the casing is divided into an inlet section 54 and an outlet section 55 by a vertical partition 56, the inlet and outlet sections lying opposite main compartments, respectively. Hot gases from the kiln are conducted from hood 27 through a duct 57 into the inlet section 54 of casing 53. The gases then flow through the tubes of the first bank 58 within main compartment 30 into sub-compartment 34 and then through the tubes of the aligned bank 59 and into a casing 60 in contact with the outer surface of container end wall 52. The gases flow transversely of the container through casing 60 and then through the tubes of bank 61 in main compartment 31, through the sub-compartment 34 within main compartment 31, and then through the tubes of bank 62 and into the outlet section 55 of casing 53. From the outlet section, the gases pass through a duct 63 to a fan and a vent stack (not shown) A plurality of tubes 64 lead from the bottom of each main compartment 30, 31 within the container to the casings 65 of respective screw conveyors, which lie beneath the main compartments and extend lengthwise of the container. Each tube 64 extends through an air chamber at the bottom of the container and its upper end lies flush with the porous top closure of the chamber. Each tube is provided with a valve 66, which is normally closed. The sub-compartments 34, the sections 54, 55 'of casing 53, and casing 60 are formed with hopper bottoms leading into the casings 65 of the adjacent screw conveyors. In the operation of the apparatus, the screw shafts 67 of the conveyors are continuously driven to advance any material entering casings 65 to the outlets 68 from the casings.

In the practice of the method by the use of the apparatus described, the material to be heated is introduced into the container 20 through inlet 23 and falls to the bottom of main compartment 30 at the outer side of partition 35. The material is aerated by air supplied through porous blocks 39 and flows beneath the lower end of partition 35 and upwardly on the inner side thereof. As the material is continuously supplied through inlet 23, the aerated material rises on the inner side of partition 35, until it flows over the top of compartment 34 into the space on the inner side of partition 36. The material then rises on the outer side of partition 36 until it reaches opening 48, through which it passes into main compartment 31. The material then flows down at the outer side of partition 36, beneath the partition, and up and over the top of compartment 34. The material then flows downward on the inner side of partition 35, beneath the lower end of the partition, and upward on the outer side of partition 35 to outlet 24. While it is preferable that the material be supplied continuously, it will be apparent that the supply may be intermittent. However, the aerated material flows through the outlet at the same rate as that at which it is supplied. In its fiow through the container from the inlet to the outlet, the travel of the material is generally counter-current to that of the treating medium, in that the material about to leave through outlet 24 is in indirect contact with the hottest gases, and the material entering the container through inlet 23 is in indirect contact with the coolest gases.

In the operation of the apparatus shown in Figs. 1-5, incl., dust carried by the hot gases will be precipitated in casing 53, the chambers 34, and casing 60, and will enter the casings 65 of the screw conveyors to be carried off. In the event that it becomes necessary to empty the container 20 for repairs or the like, the material within the container may be discharged by opening valves 66 in pipes 64, so that the material will flow into the casings 65 of the screw conveyors. Normally, when the valves 66 are closed, the portions of tubes 64 above the valves are filled with material. The auxiliary air used for fluidizing the material escapes into the upper part of container 20 and leaves through outlets 28. Any dust carried along with the escaping air is intercepted and retained by the filter within each outlet and the construction is such that the filters may be readily cleaned from time to time.

The valves 44 controlling the admission of fluidizing air into air chambers 40 may be operated by solenoids and opened and closed in turn, in accordance with the cycle. For this purpose, each solenoid may be connected in a circuit 69 across current supply lines 70, each circuit containing a switch 71, such as a mercury switch, operable by a cam 72 on a cam shaft 73 driven by a motor 74. The cams operating the switches controlling the energization of the solenoids are so formed that the solenoids are energized in sequence to open valves 44 successively and close each valve after a short period of operation. In this manner, the movement of the material through the container may be accelerated, as, for example, by first efieeting aeration of the material in main compartment 30 at the outer side of partition 35 only, after which the aeration at this point is cut off and aeration occurs in the compartment between partition am nes however, may be eifected by injecting the air through a' large number of small nozzles disposed at the location of the porous plates.

Experience has shown that, in apparatus of the kind described, the power consumption of the compressor supplying auxiliary air depends primarily on the total bottom area of the container and that the height of the body of pulverulent material above the bottom is of less importance. Accordingly, when sufiicient head room is available, it may be preferable to utilize the form of apparatus shown in Figs. 6-9, incL, in which the container 75 is elongated vertically and sub-divided by a vertical partition 76 into two main compartments, each containing an upper bank of tubes 77 and a lower bank of tubes 78. The tubes open through the end walls 79, 80, respectively, of the compartments, and the partition 76 terminates above the bottom of the container, which is formed by porous plates 81 serving as top closures for air chambers 82 separated by a central partition 83 in alignment with partition 76. Air is supplied by a line 84 to the respective chambers 82 through valved branches 85.

An inlet casing 86 attached to one end wall 87 of the container encloses the ends of tubes in the upper bank 77 at one side of the partition 76 and hot gases from kiln 88 are led into the casing through the kiln hood 89 and a duct 90. A casing 91 attached to the opposite end wall 92 of the container encloses the ends of the tubes in the upper and lower banks 77, 78 and is sub-divided by a vertical partition 91a in line with partition 76. An outlet casing 93 attached to end wall 87 of the container on the opposite side of the plane of partition 76 from casing 86 encloses the ends of the tubes 77 in the upper bank on its side of the partition. Casing 93 is connected to a duct 94 leading to a fan and a fan stack. A casing 95 is attached to end wall 87 of the container below casings 86 and 93 and encloses the ends of the tubes in the lower banks 78 on opposite sides of the I partition. The two parts of casing 91 on opposite sides of the partition within the casing are provided with hopper bottoms 96 leading to the casings 97 of respective screw conveyors, and the lower end of the casing 95 is also provided with a pair of hopper bottoms 98 leading to the casings of the conveyors. Each conveyor has abranch 99 with a valve 100 leading up through the. air chamber 82 above the conveyor and opening through the porous top wall of the chamber to the interior of the container.

The container has a frusto-conical top 101 provided with an air outlet 102 and the material is introduced into the container through an inlet 103, which leads into the container at one side of partition 76. Material is discharged from the container through an outlet 104 formed in a side wall of the container on the opposite side of partition 76 from inlet 103, and the material discharged from the outlet is led by a duct 105 through hood 89 into the upper end of the kiln.

With the construction described, the hot gases supplied from the kiln through duct 90 enter inlet casing 86 and pass through the upper bank of tubes 77 leading through the container from the casing. The gases issuing from the tubes pass into casing 91 at one side of the vertical partition 91a therein, travel downwardly, and pass through the tubes in the lower bank 78 and into casing 95. The gases travel through casing 95 transversely of the container and enter the tubes of the lower bank 78 at the other side of the partition to issue into casing 91 at the opposite side of its vertical partition. The gases then travel up through casing 91 and return through the tubes of the upper bank 77 on the inlet side of partition 76 and enter casing 93, from'which they are led off through duct 94.

The material entering the container through inlet 103 travels downwardly through the upper and lower banks of tubes at one side of partition 76 and then flows beneath the lower end of the partition and up through the tubes in the two banks at the other side of the partition to be discharged through outlet 104 and led into the kiln through duct 105. In its travel through the container, the material is aerated by air admitted through the porous top closures of the air chambers 32 and little air is required, since the area of these closures is relatively small in comparison with the amount of material being treated. Dust precipitated in the casings 91 and is discharged into the casings 97 of the screw conveyors and carried ofi. When it is necessary to empty the container, the valves in pipes 99 leading from the bottom of the container on opposite sides of partition 76 are opened and the material is admitted into the casings of the screw conveyors.

The construction shown in Figs. 10 and 11 is utilized for the cooling of a pulverulent material, such as alumina, which has been burned in a rotary kiln 106 by combustion of a fuel-primary air mixture supplied through a burner pipe 107 passing through hood 108 into which the lower end of the kiln projects. At its lower end, the hood is provided with a discharge chute 109, within which is disposed a sloping grate 110 leading, at its lower end, to a clean-out door 111. The chute leads into the top of a container 112 at one end thereof and, at its bottom, the container is provided with an air chamber 113 closed at its top by porous plates 114. A partition 115 extends downwardly from the top of the container adjacent chute 109 and terminates above the bottom of the container and a partition 116 spaced from partition 115 extends upwardly from the bottom of the container to terminate short of the, top thereof. A partition 117 spaced from partition 116 extends down fromthe top of the container and terminates nearer the bottom than partition 115. The container is provided with a material outlet 118 near its top beyond partition 117.

A bank of tubes 119 are mounted in openings in the opposite walls of the container and extend through openings in partitions 115, 116 and 117. A casing 120 attached to an end wall of the container encloses the ends of the tubes at one end of the bank and another casing 121 attached to the opposite end Wall of the container encloses the other ends of the tubes of the bank. Air for cooling is supplied by a fan 122 connected by a duct 123 to casing 121 and casing 12% is conducted to a vent stack 124.

The material issuing through the outlet 118 enters a second container 125 provided with vertical partitions 126, 127, which are spaced from the end walls of the container and terminate above the bottom thereof. central partition 128 leads upwardly from the bottom of container 125 to terminate below the top thereof. An air chamber 129, having a porous top closure 130, forms the bottom of container 125, and air is supplied to air chambers 113 and 129 in the respective containers by an air line 131. Container 125 is provided with a material outlet 132 leading from the upperend of the end wall opposite to that connected to the outlet 118 of container 112. Primary air for combustion is supplied to a mixing device 133, from which burner tube 107 extends, through a line 134 connected to the outlet of a fan 135 and the,

Water outlet header 141. The pipes are bent to extend back and forth in the spaces on opposite sides of partitions 126, 127, and 128.

In the operation of the apparatus described, the hot burned product from the kiln is discharged into hood 108 and falls upon grate 110, which retains the oversize material. The undersize material is discharged into container 112 on the outer side of partition 115, and the material is aerated by air issuing from the porous top closure 114 of the air chamber 113. The aerated material then flows up between partitions 115 and 116 and over the top of partition 116. The material then flows downwardly between partitions 116 and 117, below the lower end of partition 117, and upwardly on the outer side of partition 117 to outlet 118. The material then enters the container 125, through which it passes upwardly and downwardly in a course defined by partitions 126, 127, and 128, to the outlet 132. In its passage through container 112, the material is cooled by indirect contact with air flowing through the tubes in bank 119 and the heated air discharged into casing 121 flows up the vent stack 124 with part of the air being withdrawn by the fan 135 and supplied to the mixing device 133. In the mixing device, the air is mixed with the fuel supplied to the device through the supply pipe 142 to produce the fuelprimary air mixture fed into the kiln through the burner pipe 137. Another part of the air is withdrawn from the vent stack through duct 137 and serves as secondary air for combustion in the kiln. The material issuing from container 112 is further cooled indirectly during its passage through container 125 by water traveling through pipes 139.

In the apparatus shown in Fig. 1, the casings 53 and 60 are formed with openings aligned with the tubes 49 and 51, so that the tubes can be kept clean by the tools ordinarily used for the purpose. Similar cleaning openings are provided in casings in the form of apparatus shown in Fig. 6. In the apparatus shown in Fig. 10, casing 120 is provided with tube cleaning openings, and the material removed from the tubes may be withdrawn at the bottom of casings 120 and 121 through clean-out doors.

I claim:

1. A method of exchanging heat between pulverulent material and a flowing medium, which comprises introducing the material into a tortuous passage at one end thereof, aerating the material within the passage at a plurality of points distributed along the passage to fluidize the material, varying the intensity of the aeration elfected at said points in accordance with a cycle, and passing the medium in indirect contact with the material traveling through the passage.

2. A method of cooling pulverulent material discharged from a kiln after having been burned therein by combustion with secondary air of a fuel-primary air mixture, which comprises introducing the material discharging from the kiln into a tortuous passage at one end thereof, aerating the material within the passage to fluidize it, discharging the fluidized material from the passage at the other end thereof, cooling the fluidized material traveling through the passage by passing cooling air in indirect contact with the material to absorb heat therefrom, discharging the heated air into the atmosphere, withdrawing part of the heated air flowing toward the atmosphere and conducting it into the kiln to serve as secondary air, and withdrawing another part of the heated air flowing toward the atmosphere and mixing it as primary air with fuel to produce the fuel-primary air mix ture to be consumed in the kiln.

3. Apparatus for effecting heat exchange between pulverulent material and a flowing medium, which comprises a container having an inlet and an outlet for pulverulent material and an outlet for air, means for sub-dividing the space within the container into a plurality of vertical compartments connected together to form a continuous tortuous passage leading from the inlet to the material outlet, a plurality of air chambers at the bottom of the passage, the chambers having porous closures partly defining the passage, air supply lines leading to the individual chambers, the lines including valves, means for operating the valves to vary the quantities of air supplied to the respective chambers in accordance with a cycle, a plurality of tubes extending through the passage, and means for passing the medium through the tubes.

4. Apparatus for cooling pulverulent material discharged from a kiln after having burned therein by combustion with secondary air of a fuel-primary air mixture, which comprises a container having an inlet and an outlet for material and an outlet for air, means for subdividing the space within the container to form a tortuous passage leading from the inlet to the material outlet, means at the bottom of the container for injecting air into the material within the passage to fluidize it, a plurality of tubes extending through the passage, means for conducting burned material from the kiln into the container through the inlet, means for passing air through the tubes to remove heat from the fluidized material, means for withdrawing part of the air heated by passage through the tubes for use as primary air, and means for conducting another part of the air heated by passage through the tubes into the kiln for use as secondary air.

5. Apparatus for effecting heat exchange between pulverulent material and a fluid medium, which comprises a container having top, bottom, side, and end walls, the bottom wall being porous, an inlet and an outlet for pulverulent material, and an outlet for gas, means within the container defining a tortuous passage between the inlet and material outlet, said means including a central longitudinal partition dividing the container into main compartments and having an opening near its top adjacent one end wall of the container, a pair of spaced transverse vertical partitions sub-dividing each main compartment into subcompartments and terminating below the top of the container, a porous wall connecting the upper ends of the transverse partitions, and vertical transverse bafiles sub-dividing respective sub-compartments and having lower edges spaced from the container bottom wall, a bank of tubes in each sub-compartment opening through the transverse partition and the container end wall at opposite ends of the sub-compartment, means for supplying a fluid medium to the tubes in a sub-compartment at one end of the container, means for conducting the fluid medium away from the tubes in the other sub-compartment at said end of the container, means outside the other end of the container for connecting the tubes in the adjacent sub-compartments at said end, and means for supplying gas beneath the porous wall for diffusion therethrough into the material in said passage.

6. Apparatus for effecting heat exchange between pulverulent material and a fluid medium, which comprises a container having top, bottom, side, and end walls, the bottom wall being porous, an inlet and an outlet for pulverulent material, and an outlet for gas, means within the container defining a tortuous passage between the inlet and material outlet, said means including a central longitudinal partition dividing the container into main compartments and having an opening near its top adjacent one end wall of the container, a pair of spaced transverse vertical partitions sub-dividing each main compartment into sub-compartments and terminating below the top of the container, a porous wall connecting the upper ends of the transverse partitions, and vertical transverse baflles sub-dividing respective sub-compartments and having lower edges spaced from the container bottom wall, a bank of tubes in each sub-compartment opening through the transverse partition and the container end wall at opposite ends of the sub-compartment, a casing mounted on an end wall of the container and having an inlet section and an outlet section, one section communicating with the tubes in one sub-compartment and the other section communicating with the tubes in the other sub-compartment at said end of the container, a casing mounted on the opposite end wall of the container and connecting the tubes in the adjacent sub-compartments at said end of the container, means for supplying fluid medium to the inlet section of the first casing, and means for supplying gas beneath the porous wall for dilfusion therethrough into the material in said passage.

7. Apparatus for effecting heat exchange between pulverulent material and a fluid medium, which comprises a container having top, bottom, side, and end walls, the bottom wall being porous, an inlet and an outlet for pulverulent material, and an outlet for gas, means within the container defining a tortuous passagebetween the inlet and material outlet, said means including a central longitudinal partition dividing the container into main compartments and having an opening near its top adjacent one end wall of the container, a pair of spaced transverse vertical partitions sub-dividing each main compartment into sub-compartments and terminating below the top of the container, a porous wall connecting the upper ends of thetransverse partitions, vertical transverse baflles sub-dividing respective sub-compartments and having lower edges spaced from the container bottom wall, a bank of tubes in each sub-compartment opening through the transverse partition and the container end wall at opposite ends of the sub-compartment, means at the ends of the container for connecting the banks of tubes in series to form a passage for the fluid medium, means for supplying the medium to the tubespf the bank at one end of the passage, means for conducting away the medium from the tubes of the bank at the other end of the passage, means for supplying a gas beneath the porous wall for difiusion therethrough into the pulverulent material in said passage, and cleanout pipes opening through the bottom wall of the container for removing material therefrom.

8. Apparatus for effecting heat exchange between pulverulent material and a fluid medium, which comprises a container having top, bottom, side, and end walls, the bottom wall being porous, an inlet and an outlet for pulverulent material, and an outlet for gas, means within the container defining a tortuous passage between the inlet and material outlet, said means including a central longitudinal partition dividing the container into main compartments and having an opening near its top adjacent one end wall of the container, a pair of spaced transverse vertical partitions sub-dividing each main compartment into subcompartments and terminating below the top of the container, a porous wall connecting the upper ends of the transverse partitions, vertical transverse baflles sub-dividing respective sub-compartments and having lower edges spaced from the container bottom wall, a bank of tubes in each sub-compartment opening through the transverse partition and the container end wall at opposite ends of the sub-compartment, means at the ends of the container for connecting the banks of tubes in series to form a passage for the fluid medium, means for supplying the medium to the tubes of the bank at one end of the passage, means for conducting away the medium from the'tubes of the bank at the other end of the passage, means forming gas chambers disposed beneath the respective sub-compartments and closed at their tops by the porous wall, means for supplying gas to the chambers for escape through the porous wall into the material in the passage, said supply means including valves controlling flow to the respective compartments, and means for operating the valves cyclically to vary the flow of gas entering the material in the respective subcompartments through the porous wall.

9. Apparatus for effecting heat exchange between pulverulent material and a fluid medium, which comprises a container having top, bottom, side, and end walls, the bottom wall being porous, an inlet and an outlet for pulverulent material, and an outlet for gas, means within the container defining a tortuous passage for material traveling from the inlet to the material outlet, said means including a central vertical longitudinal partition divid ing the container into main compartments and having a lower edge spaced above the bottom wall of the container, an upper and a lower bank of tubes in each main compartment opening through the container end walls,

means at one end of the container for supplying the fluid medium to the bank of tubes at one'level in a main compartment, means at said end of the container for with drawing the medium from the bank of tubes at said level in the other main compartment, means at said end of the container for connecting the banks of tubes at the other level, means at the other end of the container for connecting the banks of tubes in the two levels in each main compartment, and means for passing gas through the porous bottom wall into the material to fluidize the latter.

10. Apparatus for cooling hot pulverulent material, which comprises a container having top, bottom, side, and end walls, the bottom wall being porous, an outlet for gas and an inlet for pulverulent material at one end of the container and an outlet for the material at the other end, means within the container defining a tortuous passage between the inlet and the material outlet, said means including a plurality of transverse vertical partitions extending alternately from the top and bottom Walls of the container and stopping short of the opposite wall, a plurality of tubes mounted in an end wall and an intermediate transverse partition and extending through other transverse partitions, means for supplying air to the tubes at one end, means for removing the air from the tubes at their other end, means for introducing hot material into the container through the inlet, means for supplying a gas beneath the porous wall for diffusion therethrough with the pulverulent material in said passage, and tubes for a cooling medium extending in a tortuous path through the passage between the intermediate partition and the container end wall having the material outlet.

References Cited in the file of this patent UNITED STATES PATENTS 1,340,267 Hildebrand May 18, 1920 2,313,052 Dean Mar. 9, 1943 2,589,730 Rathkey Mar. 18, 1952 2,590,090 De Vaney Mar. 25, 1952 2,595,822 Uggerby May 6, 1952 2,610,842 Schoenmakers et al. Sept. 16, 1952 2,629,938 Montgomery Mar. 3, 1953 

